1. Field of the Invention
The present invention relates to a speedometer for motor vehicle and, more particularly, to a speedometer gear output structure.
2. Description of the Related Art
In a conventional mechanical speedometer driving structure as shown in FIG. 7, the axle 41 of the wheel hub 4 has two lugs 43 axially extended from the end 42, a gearbox 3 is fastened to the front fork of the motorcycle to hold a driven gear 31, and a driving member 33 is coupled to the driven gear 31, and an output gear 32 meshed with the driven gear 31 and coupled to a speedometer cable 34. The driven gear 31 has two opposite flat engagement portions 311 on the periphery. The driving member 33 has two flat engagement portions 331 bilaterally disposed on the inside and respectively engaged with the flat engagement portions 311, and two peripheral lugs 332 outward extended from the periphery at two sides in reversed directions. During rotation of the axle 41 with the wheels of the motorcycle, the lugs 43 of the axle 41 move the lugs 332 of the driving member 33, thereby causing the driving member 33 to rotate the driven gear 31 and then the output gear 32, and therefore the speedometer cable 34 is driven to move the internal mechanism of the speedometer.
This mechanical speedometer driving structure has drawbacks as follows:
1. This design is a mechanical design not suitable for use with an electronic speedometer.
2. The parts of the mechanical speedometer driving structure wear quickly with use and tend to be covered with dust.
3. The mechanical design is not highly precise, unable to indicate the accurate speed of rotation of the motorcycle.